At first glance, piles of radioactive waste near Sardine Meadow don't give many clues that they surround what was once the largest uranium mine in California.

Young trees grow on the mounds, and a spring wells up in the bottom of the mining pit. The piles have been there for almost 50 years, and a half-century of rain, snow and wind has weathered them into small hills.

The only indications of possible danger are a road barricade and purple, black and yellow signs that read "CAUTION RADIATION AREA Radiation levels in this area are elevated due to uranium mining. Soil and water in this area are highly contaminated. Water should not be ingested. No access past this point. Do not drink the water."

But if these piles have been there for almost a half-century, why did the Forest Service issue a danger warning for this small area of the Stanislaus National Forest just last week?

Why did Columbia College geology students, last summer, take a field trip to the site?

Will mutant fish spring from the water?

And what is the danger to any hikers who have ventured to the remote site in the forest's Summit Ranger District?

The Juniper Uranium Mine operated from 1955 to 1966. In contrast to health-and-safety regulations that mining companies face today, prospectors in the 1950s could enter the forest under the 1872 Mining Act and just start digging, Stanislaus spokesman Jerry Snyder said.

Uranium is found naturally in the Sierra Nevada, and during the Cold War, many people thought they could find their fortunes extracting uranium from California mountainsides and selling it for power and atomic bombs.

Cleanup requirements back then were not as stringent, so dirt and rocks from the Juniper mine were just left nearby. Still, the waste was not processed at the site; it remains in its natural form, and is therefore not considered as nearly dangerous as, for example, as waste from a nuclear reactor.